Patch looks good to me.
Reviewed-by: Kajol Jain <kj...@linux.ibm.com>
Thanks,
Kajol Jain
On 9/15/23 11:07, Athira Rajeev wrote:
> Update "struct dso" to include new member "text_end".
> This new field will represent the offset for end of text
> section for a dso. For elf, this value is derived as:
> sh_size (Size of section in byes) + sh_offset (Section file
> offst) of the elf header for text.
>
> For bfd, this value is derived as:
> 1. For PE file,
> section->size + ( section->vma - dso->text_offset)
> 2. Other cases:
> section->filepos (file position) + section->size (size of
> section)
>
> To resolve the address from a sample, perf looks at the
> DSO maps. In case of address from a kernel module, there
> were some address found to be not resolved. This was
> observed while running perf test for "Object code reading".
> Though the ip falls beteen the start address of the loaded
> module (perf map->start ) and end address ( perf map->end),
> it was unresolved.
>
> Example:
>
> Reading object code for memory address: 0xc008000007f0142c
> File is: /lib/modules/6.5.0-rc3+/kernel/fs/xfs/xfs.ko
> On file address is: 0x1114cc
> Objdump command is: objdump -z -d --start-address=0x11142c
> --stop-address=0x1114ac /lib/modules/6.5.0-rc3+/kernel/fs/xfs/xfs.ko
> objdump read too few bytes: 128
> test child finished with -1
>
> Here, module is loaded at:
> # cat /proc/modules | grep xfs
> xfs 2228224 3 - Live 0xc008000007d00000
>
> From objdump for xfs module, text section is:
> text 0010f7bc 0000000000000000 0000000000000000 000000a0 2**4
>
> Here the offset for 0xc008000007f0142c ie 0x112074 falls out
> .text section which is up to 0x10f7bc.
>
> In this case for module, the address 0xc008000007e11fd4 is pointing
> to stub instructions. This address range represents the module stubs
> which is allocated on module load and hence is not part of DSO offset.
>
> To identify such address, which falls out of text
> section and within module end, added the new field "text_end" to
> "struct dso".
>
> Reported-by: Disha Goel <disg...@linux.ibm.com>
> Signed-off-by: Athira Rajeev <atraj...@linux.vnet.ibm.com>
> Reviewed-by: Adrian Hunter <adrian.hun...@intel.com>
> ---
> Changelog:
> v2 -> v3:
> Added Reviewed-by from Adrian
>
> v1 -> v2:
> Added text_end for bfd also by updating dso__load_bfd_symbols
> as suggested by Adrian.
>
> tools/perf/util/dso.h | 1 +
> tools/perf/util/symbol-elf.c | 4 +++-
> tools/perf/util/symbol.c | 2 ++
> 3 files changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
> index b41c9782c754..70fe0fe69bef 100644
> --- a/tools/perf/util/dso.h
> +++ b/tools/perf/util/dso.h
> @@ -181,6 +181,7 @@ struct dso {
> u8 rel;
> struct build_id bid;
> u64 text_offset;
> + u64 text_end;
> const char *short_name;
> const char *long_name;
> u16 long_name_len;
> diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
> index 95e99c332d7e..9e7eeaf616b8 100644
> --- a/tools/perf/util/symbol-elf.c
> +++ b/tools/perf/util/symbol-elf.c
> @@ -1514,8 +1514,10 @@ dso__load_sym_internal(struct dso *dso, struct map
> *map, struct symsrc *syms_ss,
> }
>
> if (elf_section_by_name(runtime_ss->elf, &runtime_ss->ehdr, &tshdr,
> - ".text", NULL))
> + ".text", NULL)) {
> dso->text_offset = tshdr.sh_addr - tshdr.sh_offset;
> + dso->text_end = tshdr.sh_offset + tshdr.sh_size;
> + }
>
> if (runtime_ss->opdsec)
> opddata = elf_rawdata(runtime_ss->opdsec, NULL);
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index 3f36675b7c8f..f25e4e62cf25 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -1733,8 +1733,10 @@ int dso__load_bfd_symbols(struct dso *dso, const char
> *debugfile)
> /* PE symbols can only have 4 bytes, so use .text high
> bits */
> dso->text_offset = section->vma - (u32)section->vma;
> dso->text_offset += (u32)bfd_asymbol_value(symbols[i]);
> + dso->text_end = (section->vma - dso->text_offset) +
> section->size;
> } else {
> dso->text_offset = section->vma - section->filepos;
> + dso->text_end = section->filepos + section->size;
> }
> }
>
